This is completely out of line and illegal, and you do not have to put up with it. I'm actually aghast that anyone would suggest you ask "help me to understand what I'm doing wrong" to your manager... ?!?!?!? This is simply outrageous! You are doing nothing wrong - unless you call being born with two perfectly good X chromosones "wrong"... The behaviour of your colleagues AND your management is completely unacceptable and I would suggest you tackle it head on.
You could tackle the two issues seperately, depending on how responsibility is organised in your company. As a general approach I would go in with confidence, and show you are serious.
Firstly, on pay, it is illegal to pay women less than men doing the same job. That said, in the private sector, where the lines are more grey than in the public sector, men often get higher salaries simply because they ask for it. If you're really bringing in 80% of sales, then this should be reflected in your paypacket, so I suggest you simply demand a pay rise. This is often hard for women to do (I'm not meaning to generalise, many women can be cocky as hell, but research shows that women are less comfortable making these demands) - but you can do it. It sounds as if you have a very strong case, so just put together some figures to show how much you are worth to the company, and request a significant pay rise. It's hard to work out what to ask for, but at the very least you should be asking for more than what your male colleagues earn, considering their performance. Be ready to negotiate of course, but don't forget that you should be paid according to your performance, not your age/gender etc.
Next, I would tackle the sexist behaviour firmly, but not bother with trying to make him see reason or stand up to him - we all know that when a woman tries to assert herself in this type of situation, this can easily escalate into further abuse (what's your problem, can't take a joke, must be time of the month, she's probably a man-hater, etc). Instead I would raise this with someone in authority who will take it seriously. You say previous complaints have been ignored, so I would suggest going above the person you spoke to last time, perhaps identifying someone who might take you more seroiusly. Put together a list of comments/behaviours that are unacceptable, and present them. Be very clear that this is not simple banter, but behaviour which has consistently crossed the line. You can draw on a few points here:
- you are bringing in serious money to the company, and as such are a key asset that should not be lost
- you otherwise enjoy your job and are passionate about it, but this is a serious block to you progressing
- it's illegal (do a quick google search and you'll find the references you need)
- you will have to raise it with HR/trade union/solicitors if not dealt with
Obviously, you'll use your judgement on which of these arguments is most likely to hold sway.
If you're hesitating on tackling the sexist behaviour, look at it another way: if you were the only black member of staff, and they were constantly making jokes about "bananas" or making you carry the water upstairs "like your ancesters used to", would you even QUESTION the discrimination?! I can't imagine you would, nor would anyone suggest you take a light hearted, jokey approach to tackling it.
When all is said and done, you do have to consider the possibility that you will not be taken seriously, and you may feel you have to move on. If you've got a real fight in you, you might want to speak to a solicitor, but I know most people would just want to walk away, avoid the stress, and find somewhere they are valued. It's your call. If you get a pay rise first, that will of course boost your confidence and put you in a stronger position when applying for a new role.
If you don't feel strong enough to take any of this on, it IS your right to walk away. The men wouldn't be winning. But if you can manage to muster up the courage to assert yourself, you will most definitely be a winner in my eyes, whatever happens.
And as a very final point, I would recommend reading "Lean In" by Sheryl Sandberg if you haven't already. It's a goldmine of information, really easy to read, and I found it truly motivating.
Best of luck!